Battery module, computer system having the same, and control method of the computer system

ABSTRACT

A computer system is provided. The computer system includes a device which operates according to a clock frequency, a battery unit, which comprises a plurality of battery cells, for supplying power to the device, a temperature sensor provided at a location outside of the battery unit for detecting a temperature of the battery cells, a current sensor coupled to the battery unit for detecting a value of a current supplied from the battery unit to the device, and a controller, which is coupled to the temperature sensor and the current sensor, configured to control the clock frequency of the device according to the detected temperature and the detected current value, wherein the controller is configured to decrease the clock frequency if the detected temperature is greater than a first reference value or if the detected current value is greater than a second reference value.

PRIORITY

This application is a continuation of prior application Ser. No.12/177,200, filed on Jul. 22, 2008, which claimed the benefit under 35U.S.0 §119 (a) of a Korean patent application filed on Jul. 30, 2007 inthe Korean Intellectual Property Office and assigned Serial No.10-2007-0076336, the entire disclosure of which is hereby incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate to a battery module, a computersystem having the same, and a control method of the computer system, andmore particularly, to a battery module capable of performing athrottling function, a computer system having the same, and a controlmethod of the computer system.

2. Description of the Related Art

Among computer systems, a notebook computer, a personal digitalassistant, etc., are being widely used because they are portable andusable while being moved. Such an electronic device may either use anexternal power source supplied through an AC/DC adapter or a secondarybattery charged by the adapter.

In a technical field related to the battery of the portable computer,there is much research dedicated to producing an extended battery life(EBL). For example, a narrow voltage direct current (NVDC) has beenproposed to extend the life of the battery.

Meanwhile, a maximum consumable power discharged from the battery mayvary according to the number and characteristics of battery cellsprovided therein. If power discharged from the battery is more than themaximum consumable power, an internal temperature of the battery rapidlyincreases. For example, when operations that require substantial powerare performed, the temperature of the battery increases quickly. Suchdemanding operations include reproducing a recordable medium, operatinga computer game, and the like. The maximum consumable power refers tothe maximum value within a range in which the battery can stably supplycurrent to a load.

As the temperature of the battery increases and reaches a criticalpoint, a logical fuse, a positive thermal coefficient (PTC) element,etc., which are susceptive to temperatures are cut off one afteranother, so that a system using the battery suddenly stops. In suchcase, the system may fail and unsaved data may be lost.

SUMMARY OF THE INVENTION

Accordingly, it is an aspect of the present invention to provide abattery module capable of stably supplying power, a computer systemhaving the same, and a control method of the computer system.

Another aspect of the present invention is to provide a computer systemand a control method thereof, which are capable of preventing a systemerror and a data loss due to sudden power-off

Aspects of the present invention provide a computer system including adevice which operates according to a predetermined clock frequency; abattery unit, which comprises a plurality of battery cells, to supplypower to the device; a temperature sensor to sense a temperature of thebattery cells; and a controller to control the clock frequency of thedevice according to at least the sensed temperature, wherein thecontroller decreases the clock frequency if the sensed temperature isbeyond a first preset critical point.

According to an aspect of the invention, the computer system may includea current sensor which senses current output from the battery unit,wherein the controller decreases the clock frequency if the sensedcurrent is beyond a second preset critical point.

According to an aspect of the invention, the controller may include afirst comparator which compares a voltage level corresponding to thesensed temperature with a voltage level corresponding to the firstcritical point; a second comparator which may compare a voltage levelcorresponding to the sensed current with a voltage level correspondingto the second critical point; and a logical sum operator which mayinclude a first input terminal connected to an output terminal of thefirst comparator and a second input terminal connected to an outputterminal of the second comparator, and outputs a clock control signal tothe device.

According to an aspect of the invention, the same reference voltagelevel may be input to the first comparator and the second comparator.

According to an aspect of the invention, the controller may furtherinclude a scaling factor unit that scales at least one of the voltagelevel corresponding to the sensed temperature and the voltage levelcorresponding to the sensed current as a dimension of the referencevoltage level.

According to an aspect of the invention, the device may include athermal throttling circuit to control the clock frequency according totemperature, and the thermal throttling circuit is controlled accordingto a clock control signal applied to the thermal throttling circuit bythe controller.

According to an aspect of the invention, the thermal throttling circuitmay include a divider to divide the clock frequency.

Aspects of the present invention provide a computer system including adevice which operates depending on a predetermined clock frequency; abattery unit which supplies power to the device; and a controller whichcontrols the clock frequency if at least one of current output andtemperature of the battery unit is beyond a preset critical range.

According to an aspect of the invention, the device may include athermal throttling circuit to adjust the clock frequency according totemperature, and the controller enables the thermal throttling circuit.

Aspects of the present invention provide a battery module used in acomputer system having a system part that operates depending on apredetermined clock frequency, the battery module includes a batteryunit which includes a plurality of battery cells and supplies power tothe system part; a temperature sensor which senses temperature of thebattery cells; a current sensor which senses current output from thebattery unit; a scaling factor unit which scales at least one of avoltage level corresponding to the sensed temperature and a voltagelevel corresponding to the sensed current as a dimension of a referencevoltage level; a first comparator which compares a voltage levelcorresponding to the sensed temperature with the reference voltagelevel; a second comparator which compares a voltage level correspondingto the sensed current with the reference voltage level; and a logicalsum operator which includes a first input terminal connected to anoutput terminal of the first comparator and a second input terminalconnected to an output terminal of the second comparator, and outputs aclock control signal to the system part.

Aspects of the present invention provide a power control method of acomputer system that includes a battery unit and a device operatingdepending on a predetermined clock frequency, the power control methodincluding sensing temperature of the battery unit; and decreasing theclock frequency if the sensed temperature is beyond a first presetcritical point.

According to an aspect of the invention, the power control method mayfurther include sensing current output from the battery unit; anddecreasing the clock frequency if the sensed current is beyond a secondpreset critical point.

According to an aspect of the invention, the device may include athermal throttling circuit to control the clock frequency according totemperature, and the decreasing the clock frequency includes enablingthe thermal throttling circuit; and dividing the clock frequency.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

Aspects of the present invention provide a power control method of acomputer system that comprises a battery unit and a device operatingaccording to a clock frequency, the power control method comprising:sensing a temperature of the battery unit; sensing a current output fromthe battery unit; and decreasing the clock frequency if the sensedtemperature is beyond a first preset critical point or if the sensedcurrent is beyond a second preset critical point.

According to an aspect of the present invention, a computer system isprovided. The computer system includes a device which operates accordingto a clock frequency, a battery unit, which comprises a plurality ofbattery cells, for supplying power to the device, a temperature sensorprovided at a location outside of the battery unit for detecting atemperature of the battery cells, a current sensor coupled to thebattery unit for detecting a value of a current supplied from thebattery unit to the device, and a controller, which is coupled to thetemperature sensor and the current sensor, configured to control theclock frequency of the device according to the detected temperature andthe detected current value, wherein the controller is configured todecrease the clock frequency if the detected temperature is greater thana first reference value or if the detected current value is greater thana second reference value.

According to an aspect of the present invention, a power control methodof a computer system that comprises a battery unit and a deviceoperating according to a clock frequency is provided. The power controlmethod includes detecting a temperature of the battery unit, detecting avalue of a current supplied from the battery unit to the device, anddecreasing the clock frequency if the detected temperature is greaterthan a first reference value or if the detected current value is greaterthan a second reference value.

According to an aspect of the present invention, a computer system isprovided. The computer system includes a device which operates accordingto a clock frequency, a battery unit, which comprises a plurality ofbattery cells, for supplying power to the device, a temperature sensorprovided at a location outside of the battery unit for detecting atemperature of the battery cells, a current sensor for detecting a valueof a current supplied from the battery unit to the device, and acontroller, which is connected with the temperature sensor and thecurrent sensor, configured to output a clock frequency control signal tothe device, if the detected temperature is greater than a firstreference point or if the detected current value is greater than asecond reference point, wherein the device is configured to enable athrottling operation for decreasing the clock frequency if the clockfrequency control signal outputted from the controller is received.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the present invention will becomeapparent and more readily appreciated from the following description ofthe exemplary embodiments, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a control block diagram of a computer system according to afirst exemplary embodiment of the present invention;

FIG. 2 is a control block diagram of a computer system according to asecond exemplary embodiment of the present invention;

FIG. 3 is a control block diagram of a device according to the secondexemplary embodiment of the present invention;

FIG. 4 illustrates a decrease in a clock frequency according to thesecond exemplary embodiment of the present invention;

FIGS. 5A through 5D are graphs illustrate a throttling effect accordingto the second exemplary embodiment of the present invention; and

FIG. 6 is a control flowchart of a control method of the computer systemaccording to the second exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explainaspects of the present invention by referring to the figures.

FIG. 1 is a control block diagram of a computer system according to anexemplary embodiment of the present invention. As shown therein, acomputer system includes a device 10; a battery unit 20 includingbattery cells 25; a temperature sensor 30; and a controller 40 tocontrol the device 10, the battery unit 20, and the temperature sensor30.

The device 10 operates depending on a predetermined clock frequency andcauses the computer system to perform various operations. In thisembodiment, the device 10 may include a central processing unit (CPU), agraphic chip, or the like, which includes an independent controller andoperate and process data. Here, the device 10 operates and processesdata depending on a core clock or a similar clock. The speed ofoperating and processing data increases as the frequency of the coreclock increases. Further, an interior temperature of the device 10increases as the speed of operating and processing data increases. Tocontrol the interior temperature, the device 10 can independentlycontrol the clock frequency. In other words, the device 10 according toaspects of the present embodiment has a throttling function that changesthe clock frequency to control the temperature and power.

The battery unit 20 includes the battery cells 25 and supplies thedevice with power. A rechargeable auxiliary power source, such as thebattery unit 20, is necessary to a portable computer, such as a notebookcomputer, a personal digital assistant (PDA), etc. The battery cells 25are connected in series or parallel and output power at various voltagelevels. The more battery cells 25 the battery unit 20 includes, thegreater the maximum consumable power that is output. The maximumconsumable power refers to the maximum value within a range in which thebattery can stably supply current to a load. As the speed of operatingand processing data in the device 10 increases, the power consumptionincreases and a power supply which supplies the device 10 with thepower, particularly, the battery unit 20 used as the auxiliary powersource, increases in temperature. Further, if the battery unit 20discharges power at a level greater than the maximum consumable power,the interior temperature of the battery unit 20 increases so rapidlythat internal elements of the computer system, such as a logical fuse, apositive thermal coefficient (PTC) element, etc., are cut off one afteranother. Accordingly, it is beneficial to make the battery unit 20output the power stably.

The temperature sensor 30 senses the temperature of the battery unit 20,i.e., the battery cells 25, and outputs the sensed temperature to thecontroller 40. The temperature sensor 30 may output to the controller 40a voltage level corresponding to the sensed temperature. Alternatively,the temperature sensor 30 may convert analog information about thesensed temperature into digital data and output the digital datacorresponding to the sensed temperature to the controller 40.

If the temperature of the battery cells 25 is higher than apredetermined critical point, the controller 40 decreases the clockfrequency of the device 10. Here, the controller 40 may directlydecrease the clock frequency of the device 10 or enable the throttlingfunction of the device 10. The critical point is set to be lower than atemperature managed in the battery unit 20. For example, a smarterbattery, which may be used as the battery unit 20, stops supplying powerin order to protect itself when the interior temperature thereof reachesa certain temperature (about 80° C..). In such case, the predeterminedcritical point may be set in a range from 45° C.. to 60° C. When thesensed temperature is higher than the predetermined critical point, thecontroller 40 may decrease the clock frequency of the device 10 so as tostably supply the power and preliminarily protect the computer system.

As the clock frequency becomes lower, not only the speed of operatingand processing the data decreases but also the power needed foroperating and processing the data decreases. Consequently, the amount ofcurrent supplied from the battery cells 25 decreases, and thetemperature of the battery cells 25 decreases. As the temperature of thebattery cells 25 decreases, the computer system is prevented from beingsuddenly cut off Further, data loss due to the sudden cut-off isprevented.

FIG. 2 is a control block diagram of a computer system according to anexemplary embodiment of the present invention. As shown therein, thecomputer system in this embodiment includes an adapter 110, a battery120, a first switch 131, a second switch 132, a DC/DC converter 140, acell temperature sensor 200, a current sensor 300, and a controller 400to control the foregoing and/or other elements. The controller 400includes a first scaling factor unit 410, a second scaling factor unit420, a first comparator 430, a second comparator 440, and an OR gate450, and operates similar to the controller in the above-describedembodiment associated with FIG. 1.

The adapter 110 is used as a main power source to supply DC powerconverted from AC power to the device 10. The AC power input through theadapter 110 is converted into the DC power by the DC/DC converter 140,and the DC power is supplied to the system such as the device 10 or thelike. Further, the adapter 110 supplies the battery 120 with power forcharging the battery 120 via a predetermined path (not shown).

The battery 120 includes a plurality of battery cells 125 and suppliesthe device 10 with auxiliary power. If the amount of current output fromthe battery 120 increases, the temperature of the battery cells 125increases. The temperature of the battery cells 125 may increase by amalfunction or the like in addition to or instead of to the temperatureincrease in proportion to the increased current amount.

The first switch 131 and the second switch 132 are provided as OR logicswitches to supply the device 10 with the power from either of theadapter 110 or the battery 120. If the device 10 is supplied with thepower from the adapter 110, the power from the battery 120 is cut offHowever, if there is no power from the adapter 110, the battery 120supplies the power to the device 10. As shown in FIG. 2, the firstswitch 131 and the second switch 132 are provided as a field effecttransistor (FET); however, the first switch 131 and the second switch132 are not limited thereto. Additionally, the computer system mayinclude a switch controller (not shown) to sense whether the power issupplied from the adapter 110 and transmits a control signal A to eachof the first switch 131 and second switch 132.

In this embodiment, the computer system includes a cell temperaturesensor 200 corresponding to the temperature sensor 30 of the aboveembodiment of FIG. 1.

The current sensor 300 senses the amount of current output from thebattery 120. The current sensor 300 according to this embodiment outputsa voltage level corresponding to the sensed current, but not limitedthereto. Alternatively, the current sensor 300 may output a digitalsignal corresponding to the sensed current.

The first scaling factor unit 410 scales the voltage level correspondingto the temperature sensed by the cell temperature sensor 200 as adimension of a reference voltage level Vref, and the second scalingfactor unit 420 scales the voltage level corresponding to the currentsensed by the current sensor 300 as a dimension of the reference voltagelevel Vref. The first scaling factor unit 410 and the second scalingfactor unit 420 may be provided as resistors. The same reference voltagelevel Vref is input to the first comparator 430 and the secondcomparator 440 as a reference. Thus, the voltage level input to eachcomparator 430 and 440 is scaled as a dimension of the reference voltagelevel Vref.

In another embodiment, the cell temperature sensor 200 and the currentsensor 300 may output information, such as temperature and current,instead of the voltage level. To this end, the first scaling factor unit410 and second scaling factor unit 420 may include a lookup table or thelike to convert the temperature and the current into the dimension ofthe reference voltage. Here, the lookup table includes information aboutthe voltage level corresponding to the input temperature and the inputcurrent, and each of the first scaling factor unit 410 and secondscaling factor unit 420 outputs a scaled value corresponding to thetemperature and the current.

The first comparator 430 compares a voltage level corresponding totemperature input through a non-inversion terminal with the referencevoltage level input through an inversion terminal and outputs apredetermined signal through an output terminal if the voltage levelcorresponding to the sensed temperature is higher than the referencevoltage level Vref. The second comparator 440 compares a voltage levelcorresponding to current input through the non-inversion terminal withthe reference voltage level input through the inversion terminal andoutputs a predetermined signal through an output terminal if the voltagelevel corresponding to the sensed current is higher than the referencevoltage level Vref.

The OR gate 450 is an element that implements a logical sum, of which afirst input terminal connected to the output terminal of the firstcomparator 430 and a second input terminal connected to the outputterminal of the second comparator 440. The OR gate 450 outputs a controlsignal if it receives the signal from either of the first comparator 430or second comparator 440. The control signal output from the OR gate 450is used as a clock control signal to enable the throttling function tolower the clock frequency of the device 10, such as the CPU or thegraphic chip. In other words, the controller 400 outputs the clockcontrol signal to enable the throttling function of the CPU or thegraphic chip if either of the sensed current or the sensed temperatureis beyond the critical point.

FIG. 3 is a control block diagram of the device according to anexemplary embodiment of the present invention, which explains athrottling function of the device 10. As shown therein, if it is sensedthat the interior temperature of the device 10, such as the CPU or thegraphic chip, reaches a certain critical point, a throttling operationto decrease the clock frequency is performed. To this end, the device 10includes a silicon temperature sensor 11, an internal comparator 12, anauto mode/on-demand mode selector 13, and a thermal throttling circuit14. Here, the thermal throttling circuit 14 includes a thermal controlcircuit 15 and a throttling enabler 16.

The internal comparator 12 compares the temperature input from thesilicon temperature sensor 11 with an internal reference value Vref′,and activates the thermal control circuit 15 when the sensed temperatureis higher than the reference value Vref′.

The auto mode/on-demand mode selector 13 operates depending on a basicinput/output system (BIOS) to thereby switch operation of the thermalcontrol circuit 15 between an auto mode and an on-demand mode. Here, thethermal control circuit 15 operates when the auto mode/on-demand modeselector 13 outputs an enable signal. The enable signal output from theauto mode/on-demand mode selector 13 is a precondition for operating thethermal throttling circuit 14.

The thermal control circuit 15 outputs an enable signal to thethrottling enabler 16 if the clock control signal is output from the ORgate 45 (refer to FIG. 2), and controls the throttling enabler 16 tolower the clock frequency. Here, the throttling enabler 16 changes theclock frequency and may be realized as a time-sharing divider thatdivides the clock frequency.

FIG. 4 shows waveforms to explain a decrease in a clock frequencyaccording to the exemplary embodiment of the present invention. In FIG.4, (a) illustrates the core clock frequency of the CPU or the graphicchip, which typically ranges about from 1 GHz to 2 GHz; and (b) through(d) indicate that various divisions are applied to the core clockfrequency. Specifically, (b), (c), and (d) indicate that divisions of ⅛,½ and ⅞ are applied to the clock frequency having a certain period T,respectively. In the auto mode, the division of ½ is applied to theclock frequency (refer to (c)). (e) denotes the core clock frequency fortwo periods, which is divided like (c) and in which waveforms of (a) and(c) are synthesized. The clock frequency is enabled and output for ahalf of the certain period T, but disabled and not output for the otherhalf While the clock frequency is disabled, the CPU or the graphic chiptemporarily becomes idle and thus power consumption decreases.Accordingly, the temperature of the battery 120 is decreased.

FIGS. 5A through 5D are graphs showing a throttling effect according toan exemplary embodiment of the present invention. FIG. 5A shows a powerconsumption in the battery 120 and a temperature change of the batterycell 125 as time passes in the case that the throttling function isdisabled. If a power of about 50 W, on average, 53.4 W is continuouslyconsumed from the battery cells 125, the temperature of the batterycells 125 increases as time progresses.

FIG. 5B is a graph showing the power consumption and the temperaturechange in the battery 120 in the case that the throttling function isenabled when the battery cells 125 are maintained at a temperature ofabout 45° C. or more for approximately four minutes, and FIG. 5C is agraph showing the power consumption and the temperature change in thebattery 120 in the case that the throttling function is enabled when thebattery cells 125 are maintained at a temperature of about 50° C. ormore for approximately four minutes. As shown in FIGS. 5B and 5C, if thethrottling function is enabled, a temperature increase rate of thebattery cells 125 is lowered, and the power consumption is rapidlydecreased. When the throttling function was enabled at the temperatureof about 45° C., an average power consumption was about 44.86 W. Whenthe throttling function was enabled at the temperature of about 50° C.,an average power consumption was about 45.81 W. The power consumptionbased on the enabled throttling function is less than that based on thedisabled throttling function, so that the battery 120 can stably supplypower and increase in lifespan.

The throttling function is disabled if the battery cells 125 aremaintained for a predetermined time at a temperature that is lower thanthe temperature causing the throttling function to be enabled. Forexample, in the case shown in FIG. 5B, the clock frequency may increaseif the battery cells 125 are maintained for about two minutes or moreunder the temperature of 40° C. and below; and in the case shown in FIG.5C, the clock frequency may increase if the battery cells 125 aremaintained for about two minutes or more under the temperature of 45° C.and below.

With reference to FIG. 5D, the temperatures of the battery cells 125 foreach of the above-described throttling situations are compared. As canbe seen in FIG. 5D, when the throttling function is disabled, thetemperature of the battery cells 125 continues to rise. When thethrottling function is enabled at the temperatures of 45° C. and 50° C.,it can be seen that the temperatures of the battery cells 125 increasesless than when the throttling function is disabled.

FIG. 6 is a control flowchart that explains a control method of thecomputer system according to the second exemplary embodiment of thepresent invention. As shown in FIG. 6, the controller 400 operates asfollows: First, the cell temperature sensor 200 senses the temperatureof the battery cells 125 at operation S10, and the current sensor 300senses the current output from the battery 120 at operation S20.

At operations S30 and S40, the voltage level corresponding to the sensedtemperature and the voltage level corresponding to the sensed currentare scaled as the dimension of the reference voltage level by the firstscaling factor unit 410 and the second scaling factor unit 420,respectively. At operations S50 and S60, the first comparator 430 andthe second comparator 440 determine whether the scaled voltage levelcorresponding to the temperature and the scaled voltage levelcorresponding to the current are beyond the reference voltage level,respectively.

In a determination result, if either of the voltage level correspondingto the temperature or the voltage level corresponding to the current isbeyond the reference voltage level, the controller 400 enables thethermal throttling circuit 14 provided in the device 10 at operationS70.

The thermal control circuit 15 of the thermal throttling circuit 14receives the clock control signal corresponding to the enable signal,and controls the throttling enabler 16 to divide the clock frequency atoperation S80.

The temperature control circuit 15 may control the throttling enabler 16according to a logical sum between an activation signal from theinternal comparator 12 and the clock control signal from the controller400, but the temperature control circuit 15 is not limited thereto assuch control is not necessary.

Alternatively, the reference voltage levels Vref input to the firstcomparator 430 and the second comparator 440 may be different from eachother. As such, the reference voltage level Vref to be input to thefirst comparator 430 is set as a level corresponding to a criticaltemperature at which consumable power output from the battery 120 is nothigher than the maximum consumable power. Likewise, the referencevoltage level Vref to be input to the second comparator 440 is set as alevel corresponding to a critical current at which consumable poweroutput from the battery 120 is not higher than the maximum consumablepower. Accordingly, at least one of the first scaling factor unit 410and the second scaling factor unit 420 may be not needed.

Further, the adapter 110, the switches 131 and 132, and the DC/DCconverter 140 may be separated from the computer system and may beprovided in a battery module. In such case, the clock control signaloutput from the controller 400 may be transmitted to the device 10 via ageneral system bus. Alternatively, other elements except the battery 120may be provided in the computer system.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

What is claimed is:
 1. A computer system, comprising: a device whichoperates according to a clock frequency; a battery unit, which comprisesa plurality of battery cells, for supplying power to the device; atemperature sensor provided at a location outside of the battery unitfor detecting a temperature of the battery cells; a current sensorcoupled to the battery unit for detecting a value of a current suppliedfrom the battery unit to the device; and a controller, which is coupledto the temperature sensor and the current sensor, configured to controlthe clock frequency of the device according to the detected temperatureand the detected current value, wherein the controller is configured todecrease the clock frequency if the detected temperature is greater thana first reference value or if the detected current value is greater thana second reference value.
 2. The computer system according to claim 1,wherein the controller is configured to control the battery unit to stopsupplying the power if the temperature detected by the temperaturesensor is greater than a third reference value which is greater than thefirst reference value.
 3. The computer system according to claim 1,wherein the controller is configured to decrease the clock frequency ifthe detected temperature is maintained for preset time at a temperaturegreater than the first reference value.
 4. The computer system accordingto claim 3, wherein the controller is configured to increase the clockfrequency if the detected temperature is maintained for preset time at atemperature that is lower than the first reference value, after theclock frequency is decreased.
 5. The computer system according to claim1, wherein the device comprises a thermal throttling circuit to controlthe clock frequency according to a temperature, the thermal throttlingcircuit configured to control the clock frequency according to a clockcontrol signal applied to the thermal throttling circuit by thecontroller.
 6. The computer system according to claim 5, wherein thethermal throttling circuit is configured to control to enable the clockfrequency for preset time of certain period T and to disable the clockfrequency for remaining time of certain period T.
 7. The computer systemaccording to claim 1, wherein the controller comprises: a firstcomparator for comparing a voltage level corresponding to the detectedtemperature with a voltage level corresponding to the first referencevalue; a second comparator for comparing a voltage level correspondingto the detected current value with a voltage level corresponding to thesecond reference value; and a logical sum operator which comprises afirst input terminal connected to an output terminal of the firstcomparator and a second input terminal connected to an output terminalof the second comparator, and outputs a clock control signal to thedevice.
 8. The computer system according to claim 7, wherein a samereference voltage level is input to the first comparator and the secondcomparator.
 9. The computer system according to claim 8, wherein thecontroller further comprises a scaling factor unit that scales at leastone of the voltage level corresponding to the detected temperature andthe voltage level corresponding to the detected current value as adimension of the reference voltage level.
 10. A power control method ofa computer system that comprises a battery unit and a device operatingaccording to a clock frequency, the power control method comprising:detecting a temperature of the battery unit; detecting a value of acurrent supplied from the battery unit to the device; and decreasing theclock frequency if the detected temperature is greater than a firstreference value or if the detected current value is greater than asecond reference value.
 11. The method according to claim 10, whereindetecting the temperature is performed by a temperature sensor which islocated outside of the battery unit.
 12. The method according to claim10, further comprising: controlling the battery unit to stop supplyingthe power if the detected temperature of the battery unit is greaterthan a third reference value which is greater than the first referencevalue.
 13. The method according to claim 10, wherein decreasing theclock frequency comprises decreasing the clock frequency if the detectedtemperature is maintained for preset time at a temperature greater thanthe first reference value.
 14. The method according to claim 13, furthercomprising: increasing the clock frequency if the detected temperatureis maintained for preset time at a temperature that is lower than thefirst reference value, after the clock frequency is decreased.
 15. Themethod according to claim 10, wherein the device comprises a thermalthrottling circuit to control the clock frequency according to atemperature, the thermal throttling circuit configured to control toenable the clock frequency for preset time of certain period T, and todisable the clock frequency for remaining time of certain period T. 16.The method according to claim 10, further comprising: comparing avoltage level corresponding to the detected temperature of the batteryunit with a voltage level corresponding to a first reference value toyield a first result; comparing a voltage level corresponding to thecurrent output with a voltage level corresponding to a second referencevalue to yield a second result; summing, by a logical summing operator,the first result and the second result, and outputting a clock controlsignal by the logical summing operator to the device in response to thesumming
 17. The method according to claim 16, further comprising:scaling a voltage level corresponding to the detected temperature as adimension of a reference voltage level, and wherein the clock frequencyis decreased if the scaled voltage level is greater than the referencevoltage level.
 18. A computer system, comprising: a device whichoperates according to a clock frequency; a battery unit, which comprisesa plurality of battery cells, for supplying power to the device; atemperature sensor provided at a location outside of the battery unitfor detecting a temperature of the battery cells; a current sensor fordetecting a value of a current supplied from the battery unit to thedevice; and a controller, which is connected with the temperature sensorand the current sensor, configured to output a clock frequency controlsignal to the device, if the detected temperature is greater than afirst reference point or if the detected current value is greater than asecond reference point wherein the device is configured to enable athrottling operation for decreasing the clock frequency if the clockfrequency control signal outputted from the controller is received.